There is a fundamental gap in our understanding of why skin diseases, such as chronic urticaria and psoriasis, are aggravated by stress. The long-term goal of this research is to define the role of mast cells in inflammatory diseases. The objective of this application is to identify the contribution of the corticotropin-releasing hormone (CRH) receptors and neurotensin (NT) receptor-1 in stress-induced skin mast cell activation and increased vascular permeability, using both a mouse model and human skin biopsies. Restraint stress increases skin mast cell degranulation, CRH content and vascular permeability;these effects are unaffected in SP-/- and CRH-/- mice, but absent in W7WV mast cell deficient mice. CRH increases vascular permeability when injected intradermally in mice, but this effect is blocked by the NTR-1 antagonist SR48692 and is absent in NT -/- mice, demonstrating the critical role of NT. Stress may elicit release of CRH and NT from dorsal root ganglia (DRG) skin terminals and activate mast cells expressing functional CRHR and NTR-1. The clinical relevance of these findings is evidenced by increased expression of CRHR-1 and histidine decarboxylase (HOC) in affected skin from patients with chronic urticaria, indicating the involvement of CRH and mast cells. The central hypothesis is that CRH released in the skin by acute stress, alone or together with NT, activates mast cells leading to increased vascular permeability and neurogenic inflammation. Guided by strong preliminary data, this hypothesis will be tested by pursuing four specific aims: (1) Determine the importance of CRHR and NTR-1 on stress and intradermal CRH-induced skin mast cell activation and vascular permeability using CRHR-1-/-, CRHR-2-/-, double CRHR -/-, or NTR-1-/- mice. (2) Determine if CRHR or NTR-1 need to be expressed on skin mast cells by reconstituting W/WV mast cell deficient mice with bone marrow progenitors from the appropriate CRHR-/- or NTR-1 -/- mice. (3) Investigate the expression of CRHR and NTR-1 in human skin biopsies from atopic dermatitis, chronic urticaria and psoriasis patients, and correlate findings with serum CRH levels and extent of stress by using the State-Trait Anxiety Inventory (STAI). (4) Investigate the effect of CRH and NT on release from human skin biopsy explants and human cultured mast cells of proinflammatory cytokines. Our approach is innovative because it utilizes knockout mice and reconstitution techniques to understand how stress-derived neuropeptides contribute to skin inflammation, and employs novel methods of assaying mediator release. The proposed research is significant because it is expected to advance understanding of how acute stress increases skin vascular permeability and neurogenic inflammation. This is an important and under investigated area of skin pathophysiology that has potential applicability to understanding the pathogenesis of skin diseases and screening compounds that may develop into novel and effective treatments.